1. Field of the Invention
The present invention relates to a method of replacing and operating a refrigeration system or an air conditioning system employing the refrigeration system. Further, the present invention relates to a method of replacing a refrigerant in a refrigeration system.
More particularly, the present invention relates to a refrigeration system which employs a refrigeration cycle (hereinafter referred to as a xe2x80x9crefrigeration systemxe2x80x9d) and enables replacement of a heat source unit with a new one or replacement of a heat source unit and an indoor unit with new ones and which enables replacement of a previous-employed refrigerant with a new refrigerant of different type without involvement of replacement of at least connecting pipes for connecting the heat source unit with the indoor unit. The present invention further relates to a method of operating such refrigeration system.
2. Background Art
FIG. 27 shows a popular standalone-type refrigeration system which has already been used. In FIG. 27, reference symbol AA designates a heat source unit accommodating a compressor 1, a four-way valve 2, a heat exchanger 3 at a heat-source-unit side, a first control valve 4, a second control valve 7, and an accumulator 8. Reference symbol BB designates an indoor unit including a flow rate regulator 5 (or a flow rate control valve 5) and a heat exchanger 6 at a user-side. The heat source unit AA and the indoor unit BB are remotely separated from each other and are interconnected together by way of a first connecting pipe CC and a second connecting pipe DD, thus constituting a refrigeration system (i.e., a system employing the refrigeration cycle).
One end of the first connecting pipe CC is connected to the heat exchanger 3 on the heat-source-unit-side by way of the first control valve 4, and the other end of the first connecting pipe CC is connected to the flow rate regulator 5. One end of the second connecting pipe DD is connected to the four-way valve 2 by way of the second control valve 7, and the other end of the second connecting pipe DD is connected to the heat exchanger 6 on the user-side. Further, an oil return hole 8a is formed in a lower portion of a U-shaped outlet pipe of the accumulator 8.
The circulation of a refrigerant within the refrigeration system will now be described by reference to FIG. 27. In the drawing, solid arrows depict the circulation of the refrigerant during a cooling operation, and dotted arrows depict the circulation of the refrigerant during a heating operation.
First will be explained the circulation of a refrigerant during a cooling operation. The refrigerant is compressed by the compressor 1 to assume the form of a hot, high-pressure gas; flows via the four-way valve 2 into the heat-source-unit-side heat exchanger 3, where the gaseous refrigerant exchanges heat with a heat source medium, such as water or air; and is condensed. The thus-condensed refrigerant flows, via the first control valve 4 and the first connecting pipe CC, to the flow rate regulator 5, where the refrigerant is decompressed to a low-pressure two-phase state. By way of the user-side heat exchanger 6, the refrigerant exchanges heat with a user-side medium, such as air, and evaporates. The thus-evaporated refrigerant returns to the compressor 1 via the second connecting pipe DD, the second control valve 7, the four-way valve 2, and the accumulator B.
Next will be explained the circulation of the refrigerant during a heating operation. The refrigerant is compressed by the compressor 1 to assume the form of a hot, high-pressure gas; and flows via the four-way valve 2, the second control valve 7, and the second connecting pipe DD into the user-side heat exchanger 6, where the gaseous refrigerant exchanges heat with a heat source medium, such as air, and is condensed. The thus-condensed refrigerant flows to the flow rate regulator 5, where the refrigerant is decompressed to assume a low-pressure two-phase state. By way of the first connecting pipe CC, the first control valve 4, and the heat-source-unit-side heat exchanger 3, the refrigerant exchanges heat with a heat-source-unit-side medium, such as air or water, and is vaporized. The thus-vaporized refrigerant returns to the compressor 1 via the four-way valve 2 and the accumulator 8.
Chlorofluorocarbon (CFC) or a hydrochlorofluorocarbon (HCFC) has been used as a refrigerant of such a refrigeration system. However, since chlorine contained in molecules of a CFC or HCFC depletes the ozone layer of the stratosphere, use of CFC has been phased out. Moreover, production of HCFCs has been subjected to regulation.
A refrigeration system using a hydrofluorocarbon (HFC) whose molecules do not contain chlorine has already been put into actual use. In a case where a refrigeration system using a CFC or HCFC (hereinafter referred to also as a xe2x80x9cCFC/HCFC-using refrigeration system) is deteriorated and becomes unusable, the refrigeration system must be replaced with a new refrigeration system using an HFC (hereinafter referred to also as an xe2x80x9cHFC-using refrigeration system), because use of CFCs has been phased out and production of HCFCs is regulated.
The heat source unit AA and the indoor unit BB for use with an HFC employ refrigeration oil, an organic material, and a heat exchanger which differ in type from those employed by the heat source unit AA and the indoor unit BB for use with an HCFC. Therefore, the refrigeration oil, the organic material, and the heat exchanger must be replaced with those designed specifically for use with an HFC. Further, let us assume that the heat source unit AA and the indoor unit BB for use with a CFC or HCFC have deteriorated and hence must be replaced with new ones. The heat source unit AA and the indoor unit BB can be replaced with new ones with comparative ease.
In a case where the first connecting pipe CC and the second connecting pipe DD interconnecting the heat source unit AA and the indoor unit BB are lengthy and embedded in a structure, such as a pipe shaft or a ceiling, difficulty is encountered in replacing the connecting pipes with new pipes. Further, these connecting pipes are not susceptible to deterioration, and hence if the first connecting pipe CC and the second connecting pipe DD used in the CFC/HCFC-using refrigeration system are usable, in their present forms, piping work can be facilitated.
In the first connecting pipe CC and the second connecting pipe DD used in the CFC/HCFC-using refrigeration system, there still remains residual mineral oil which has been used as a refrigeration oil for the CFC/HCFC-using refrigeration system (hereinafter called a xe2x80x9cCFC/HCFC refrigeration oil), CFC/HCFC, or depleted substances).
FIG. 28 is a graph showing critical solubility curves which represent the solubility of an oil for use with an HFC (hereinafter called simply as an xe2x80x9cHFC refrigeration oilxe2x80x9d) in an HFC refrigerant when the HFC refrigeration oil is mixed with a mineral oil. The horizontal axis of the graph represents amount of oil (wt. %), and the vertical axis of the graph represents temperature (xc2x0 C.).
As shown in FIG. 28, if a predetermined amount of mineral oil is mixed into an oil for use with a refrigeration system using an HFC (hereinafter also called an xe2x80x9cHFC refrigeration oilxe2x80x9d) (e.g., a synthetic fluid such as an ester oil or an ether oil), the refrigeration oil loses compatibility with an HFC refrigerant. If a puddle of liquid refrigerant is present in the accumulator 8, the HFC refrigeration oil is isolated from and suspended in the liquid refrigerant. Accordingly, the HFC refrigeration oil does not return to the compressor 1 by way of the oil return hole 8a formed in the lower portion of the accumulator 8, thus causing a sliding section of the compressor 1 to seize up.
If a mineral oil is mixed into the HFC refrigeration oil, the HFC refrigeration oil becomes deteriorated. Alternatively, if a CFC or HCFC is mixed into the HFC refrigeration oil, a chlorine component contained in the CFC or HCFC deteriorates the HFC refrigeration oil; otherwise, a chlorine component contained in sludge formed from a depleted substance of the CFC/HCFC refrigeration oil may deteriorate the HFC refrigeration oil.
The first connecting pipe CC and the second connecting pipe DD are cleansed with a cleaning fluid (HCFC 141b or HCFC 225) through use of cleaning equipment (this method will hereinafter be called a xe2x80x9cfirst cleaning methodxe2x80x9d).
Another cleaning method described in Japanese Patent Laid-Open No. 83545/1995 (hereinafter referred to as a xe2x80x9csecond cleaning methodxe2x80x9d) has already been put forward. As shown in FIG. 29, the heat source unit AA for use with an HFC (hereinafter also called an xe2x80x9cHFC heat source unitxe2x80x9d), the indoor unit BB for use with an HFC (hereinafter also called an xe2x80x9cHFC indoor unitxe2x80x9d), the first connecting pipe CC, and the second connecting pipe DD are interconnected without use of the cleaning equipment (step 100). After having been charged with an HFC refrigerant and an HFC refrigeration oil (step 101), the refrigeration system is operated for cleaning (step 102). Subsequently, the HFC refrigerant and the HFC refrigeration oil remaining in the refrigeration system are recovered, and the refrigeration system is charged with a new refrigerant and a new refrigeration oil (step 103). The refrigeration system is again operated for cleaning. These operations are repeated a predetermined number of times (steps 104 and 105).
The first conventional cleaning method has encountered the following problems. Specifically, since an HCFC which depletes the ozone layer is used as a cleaning fluid, the first method is inconsistent with the plan to change the refrigerant of the refrigeration system from an HCFC to an HFC. Particularly, HCFC 141b has an ozone layer depletion factor of 0.11 and poses a big problem.
A second problem of the first method is that a cleaning fluid is not completely safe in terms of flammability and toxicity. HCFC 141b is flammable and has low toxicity. HCFC 225 is not flammable but has low toxicity.
A third problem of the first method is that the cleaning fluid has a high boiling point (HCFC 141b has a boiling point of 32xc2x0 C., and HCFC 225 has a boiling point of 51.5 to 56.1xc2x0 C.). When the outside air temperature is lower than the boiling point, which is likely to be the case during the winter, the cleaning fluid remains, in a liquid state, in the first connecting pipe CC and the second connecting pipe DD after cleaning. Since the cleaning fluid is made of an HCFC, the chlorine component contained in the cleaning fluid deteriorates the HFC refrigeration oil.
A fourth problem of the first method is a necessity for recovering the total amount of cleaning fluid so as to prevent environmental destruction. If the refrigeration system is cleansed again through use of high-temperature nitrogen gas so as to prevent occurrence of the third problem, the cleansing operation requires expenditure of much effort.
The second conventional cleaning method has encountered the following problems. The embodiment described in Japanese Patent Laid-Open No. 83545/1995 requires three-time cleaning operation using the HFC refrigerant. Further, the HFC refrigerant used in the cleaning operation contains impurities, and hence the recovered HFC refrigerant cannot be reused in its present form. The cleaning operation requires HFC refrigerant in an amount of three times that usually used for charging a refrigeration system, and hence the second method imposes problems in relation to cost and the environment.
A second problem of the second method is that the refrigeration oil is replaced with new refrigeration oil after cleaning operation of the refrigeration system, which requires a refrigeration oil in an amount of three times that usually used for charging a refrigeration system, thus imposing problems in relation to cost and the environment. The HFC refrigeration oil is an ester oil or an ether oil and possesses a high hydroscopic property, and hence control of moisture content of a refrigeration oil for replacement purpose is also required. Further, the refrigeration oil is charged by a human worker who cleans the refrigeration system, and there may arise a shortage or excess in the amount of refrigeration oil to be charged, which in turn induces a problem in subsequent operation of the refrigeration system (in the event of the refrigeration system having been excessively charged with a refrigeration oil, there may arise destruction of a compression section and overheating of a motor, whereas in the event of the refrigeration system having been insufficiently charged with a refrigeration oil, a lubrication failure may arise).
The present invention has been conceived to solve these problems of the conventional methods and is aimed at providing a method of constructing a refrigeration system which enables replacement of an existing refrigeration system using an environmentally-hazardous refrigerant with a refrigeration system using an environmentally-friendly refrigerant, a method of replacing a refrigerant, and a method of operating the refrigeration system for cleaning purposes.
According to one aspect of the present invention, a method of operating a refrigeration system is provided in which an old refrigerant used in a refrigerant circuit is replaced with a new refrigerant. The refrigerant circuit comprises a compressor, a heat-source-unit-side heat exchanger, a user-side heat exchanger, a first connecting pipe interconnecting one end of the heat-source-unit-side heat exchanger and one end of the user-side heat exchanger, a second connecting pipe interconnecting the other end of the user-side heat exchanger and the compressor, and an extraneous-matter trapping apparatus for trapping extraneous matter contained in the refrigerant inserted in the refrigerant circuit upstream of the compressor. In the refrigeration system, after the old refrigerant is replaced, the new refrigerant is caused to flow while the compressor is taken as a drive source, thereby cleaning the refrigerant circuit. (c1)
According to another aspect of the present invention, a method is provided for replacing an old refrigeration system to a new refrigeration system. The old refrigeration system uses first refrigerant and comprises a first heat source unit including at least a compressor and a heat-source-unit-side heat exchanger, an indoor unit including at least a user-side heat exchanger and a flow rate regulator, and first and second connecting pipes interconnecting the first heat source unit and the indoor unit, to thereby constitute a refrigerant circuit. Wherein, the new refrigeration system is constituted by means of replacing at least the first heat source unit with a second heat source unit. The second heat source unit uses second refrigerant and comprises a heat source unit refrigerant circuit including at least a heat source refrigerant and a heat-source-unit-side heat exchanger, an oil separation apparatus which is inserted in the heat source unit refrigerant circuit, which separates refrigeration oil from the refrigerant of the heat source unit refrigerant circuit, and which returns the refrigeration oil to the compressor, and extraneous-matter trapping means for separating and trapping extraneous matter from the refrigeration oil separated by the oil separation apparatus. Further, the first refrigerant is replaced with the second refrigerant. (c5)
According to another aspect of the present invention, a refrigeration system comprises at least a compressor, a heat-source-unit-side heat exchanger, a user-side diaphragm, a user-side heat exchanger, an accumulator, a first connecting pipe for interconnecting the heat-source-unit-side-unit heat exchanger and the user-side diaphragm, and a second connecting pipe for interconnecting the user-side heat exchanger and the compressor. Wherein, at least the compressor and the heat-source-unit-side heat exchanger are replaced with a new compressor and a new heat-source-unit-side heat exchanger which use HFC refrigerant. A refrigerant circuit is constituted by use of at least the first and second connecting pipes, as well as by use of the user-side heat exchanger and the user-side diaphragm. A refrigerant used in the refrigeration system is replaced with HFC refrigerant. Further, a refrigeration oil is used which has no mutual solubility with respect to HFC refrigerant or has very low mutual solubility. (c7)
Other and further objects, features and advantages of the invention will appear more fully from the following description.